1. Field of the Invention
The present invention relates generally to automotive steering system. More particularly, it pertains to apparatus for hydraulically sealing and connecting transfer lines to a tube and housing.
2. Description of the Prior Art
A power-assisted, rack and pinion steering system for automotive applications includes a steering shaft controlled manually by the vehicle operator by rotating the vehicle's steering wheel. The steering shaft is connected through a flexible coupling to a pinion gear, which is driveably engaged with a rack located in a relatively thick walled tube. The rack extends laterally from a housing to a mechanism that steers the vehicle's wheels.
The tube also contains a hydraulic double-acting piston, which is secured to the rack. A piston moves in a cylinder located in the tube in response to differential pressure across the piston. A control valve alternately pressurizes and vents the opposite faces of the cylinder in response to rotation of the steering wheel and pinion gear. As the rack moves in opposite linear directions along the tube in response to rotation of the steering wheel, a net hydraulic pressure force produced on the piston assists the vehicle operator to steer the wheels by adding to the force on the rack applied manually by the vehicle operator. In this way, the operator's effort and the degree to which the steering wheel is rotated in order to produce a desired change in direction are reduced.
Transfer lines carry pressurized hydraulic fluid from the housing to the cylinder located in the tube. Generally the housing is formed of cast aluminum, but the tube and transfer lines are of steel. The physical property differences and strength dissimilarities of the metals add to the complicity of the connections at each end of the transfer lines.
There is a long felt need in steering gear design for an efficient, low cost technique to connect the transfer lines to the outer surface of the tube without use of weld stud adapters attached to the rack tube and providing a screw-in attachment to the transfer lines. It is desired that the transfer lines be connected to the aluminum housing using a screw-in attachment, or a metallic bond to a threaded insert, or a slip attachment that is hydraulically sealed.